A driving circuit of a display panel mainly includes gate lines and data lines. When a gate line is at a high level, a thin-film transistor is turned on, and a data line charges a pixel electrode; when the gate line is at a low level, the thin-film transistor is turned off, the data line stops charging the pixel electrode, and a storage capacitor supplies power to the pixel electrode.
Due to coupling effect of a common electrode, a certain voltage drop occurs across a data line. Influenced by the voltage drop, voltages at both terminals of the data line are not uniform, which leads to phenomena of picture flickering on the display panel.
A current solution is as follows: for a substrate in a chip-on-glass (COG) state, a flexible printed circuit board (FPC) is manually pressed onto the substrate using a jig such that goldfingers on the flexible printed circuit board are aligned with electrodes on the substrate. Then a voltage of the common electrode is pre-written into a driving chip by multi-time programmable (MTP) writing operation, to offset the voltage drop across the data line.
According to the prior art, the substrate is first placed on a jig, a pressure head with the flexible printed circuit board mounted thereon is then pressed onto the substrate manually. The screen is switched to a jitter test picture after being lightened, a value of the voltage of the common electrode is adjusted until the picture jitter is minimized, and the adjusted value of the voltage of the common electrode is then written into the driving chip.
Because alignment accuracy of the manual pressing is not high, the goldfingers on the flexible printed circuit board and the electrodes on the substrate cannot be aligned completely accurately as a result. For example, as shown in FIG. 1, there is an alignment deviation between a goldfinger 1 and an electrode 2. In this case, the circuit can still be turned on, and the screen can still be lightened as well, but a contact resistance at this time between the goldfinger 1 on the flexible printed circuit board and the electrode 2 on the substrate differs from a contact resistance between the goldfinger 1 on the flexible printed circuit board laminated automatically by a machine and the electrode 2 on the substrate during a subsequent manufacturing process.
FIG. 2 schematically illustrates a case where a goldfinger 1 and an electrode 2 laminated automatically by a machine are aligned accurately. In this case, the contact resistance between the goldfinger 1 and the electrode 2 is different from the contact resistance between the goldfinger 1 and the electrode 2 shown in FIG. 1. This will result in that the voltage of the common electrode written into the driving chip in a COG state is not suitable for a subsequent FPC-on-glass (FOG) state, thus the phenomena of picture flickering cannot be truly improved.